The Lloyd's building, now a quarter of a century old, is as much part of the City of London's landscape as Wren's churches. Photograph: Matt Cardy/Getty Images

The Lloyd's building is a case of a venerable institution trying to update its image by hiring an exciting modern architect. In the 1980s Lloyd's of London, then aged 300 or so, commissioned Richard Rogers to design their new headquarters. They were sold on his idea that, by putting pipes, lifts, stairs and toilets on the outside, in theoretically removable capsules, the building could be reconfigured at will. It didn't work out like that: the external shape has barely changed, and it is now likely to be listed as a historic building, which makes it as much a fixed monument as a Wren church. But as an excuse for visual dazzle, for a structure of gothic intricacy variously compared to a motorcycle engine and a coffee percolator, Rogers's concept worked brilliantly. Inside the building is more sober than the outside, but still grand, with an atrium plunging down from a glass barrel vault, criss-crossed by escalators, to a double height trading floor at the bottom. Here, in its incongruous dark wood baldachin, hangs the Lutine Bell, historically rung when a ship went missing.